Minimizing metal corrosion during post metal solvent clean

ABSTRACT

The inventive method provides a wet cleaning of semiconductor devices on semiconductor wafers after photoresist is stripped. Semiconductor wafers are placed into a centrifuge carriage of a processing chamber. The centrifuge carriage rotates the semiconductor wafers. N-methylpyrrolidine heated to a temperature between 65° C. and 85° C. is sprayed onto the semiconductor wafers. Next N-methylpyrrolidine at room temperature is sprayed onto the semiconductor wafers. Finally, water at room temperature is sprayed onto the semiconductor wafers. The inventive method provides high throughput cleaning without undue corrosion or damage to metal layers.

FIELD OF THE INVENTION

[0001] The present invention relates the cleaning of etched residue fromsemiconductor devices. More particularly, the invention relates to thewet cleaning of etched residue from semiconductor devices.

BACKGROUND OF THE INVENTION

[0002] In the manufacture of semiconductor devices, photoresist isapplied to a surface to create an etch barrier. Parts not covered by thephotoresist are etched away. The photoresist is then stripped away.Remaining photoresist and the etching residue is then cleaned, oftenthrough a wet cleaning process. If the solvent used in the wet cleaningprocess is too aggressive, the solvent may attack or corrode metallayers of the semiconductor devices. If the solvent used in the wetcleaning process is not aggressive enough, it may provide a slowthroughput or insufficient residue removal. As device size decreases,solvent attack or corrosion of metal layers and residue are more likelyto damage a semiconductor device.

[0003] It would be advantageous to provide a wet cleaning processes thatreduces solvent attack and corrosion of metal layers, which does notreduce residue removal and device throughput.

BRIEF SUMMARY OF THE INVENTION

[0004] It is an object of the invention to provide a wet cleaningprocess that reduces solvent attack and corrosion of metal layers,without reducing residue removal and device throughput.

[0005] Accordingly, the foregoing object is accomplished providing asolvent spray at an elevated temperature, then providing a spray of thesame solvent at a lower temperature close to room temperature, and thenproviding a water rinse.

[0006] Other features of the present invention are disclosed or apparentin the section entitled: “DETAILED DESCRIPTION OF THE INVENTION.”

BRIEF DESCRIPTION OF DRAWINGS

[0007] For a fuller understanding of the present invention, reference ismade to the accompanying drawings wherein:

[0008]FIG. 1 is a schematic view of a wafer cleaning rinse system thatis used in the practice of the invention.

[0009]FIG. 2 is a cross-sectional view of an unfinished semiconductordevice prior to being etched.

[0010]FIG. 3 is a cross-sectional view of the unfinished semiconductordevice, shown in FIG. 2, after etching.

[0011]FIG. 4 is a cross-sectional view of the unfinished semiconductordevice, shown in FIG. 3, after plasma stripping and solvent strippingand prior to the inventive process.

[0012]FIG. 5 is a cross-sectional view of the unfinished semiconductordevice, shown in FIG. 4, after undergoing the inventive process.

[0013]FIG. 6 is a cross-sectional view of the of the unfinishedsemiconductor device, shown in FIG. 5, after an intermetallic dielectriclayer has been deposited over the stacks.

[0014] Reference numbers refer to the same or equivalent parts of thepresent invention throughout the several figures of the drawing.

DETAILED DESCRIPTION OF THE INVENTION AND BEST MODE OF THE INVENTION

[0015]FIG. 1 is a schematic view of a wafer cleaning system 10. Thewafer cleaning system 10 comprises a processing chamber 12, a first tank14 in fluid connection with the processing chamber 12 through a firstvalve 16, a second tank 18 in fluid connection with the processingchamber 12 through a second valve 20, and a third tank 22 in fluidconnection with the processing chamber 12 through a third valve 24. Afirst temperature control 15 is connected to the first tank 14. A secondtemperature control 19 is connected to the second tank 18. A thirdtemperature control 23 is connected to the third tank 22. The processingchamber 12 comprises at least one spray nozzle 26 and a centrifugecarriage 28.

[0016] In operation, prior to the inventive cleaning step, a waferundergoes several steps to build semiconductor devices. FIG. 2 is across-sectional view of an unfinished semiconductor device 110 on asemiconductor wafer 30, which has an upper surface 112. An oxide layer113 is deposited on the upper surface 112. A first refractory metallayer 115 is deposited on the oxide layer 113. In this example, thefirst refractory metal layer 115 is made of a refractory metal chosenfrom the group consisting of titanium Ti, titanium nitride TiN,titanium/titanium nitride Ti/TiN. An aluminum alloy layer 116 isdeposited on the first refractory metal layer 115. A second refractorymetal layer 118 is deposited on the aluminum alloy layer 116. In thisexample, the second refractory metal layer is made of a refractory metalchosen from the group consisting of Ti, TiN, Ti/TiN. A photoresist mask120 is placed on the second refractory metal layer 118.

[0017] The semiconductor device 110 then is subjected to a plasmaetching to provide a metal etch. In plasma etching a power sourcecreates a radio frequency field, which is used to energize etchant gasesto a plasma state. The etchant gases attack the metal layer etching awaythe parts of the first refractory metal layer 115, aluminum alloy layer116, second refractory metal layer 118, and the oxide layer 112 that arenot covered by the photoresist mask 120.

[0018]FIG. 3 is a cross sectional view of the part of the unfinishedsemiconductor device 110 after it has gone through the metal etch. Twostacks 122 are formed with each stack comprising an oxide layer 113, afirst refractory metal layer 115, an aluminum alloy layer 116, and asecond refractory metal layer 118, capped by the photoresist mask 120.The etchant gasses deposit some of the photoresist onto the side wallsof the stacks 122, creating sidewall polymer residue 124.

[0019] The semiconductor device 110 is then subjected to a plasma stripand then a solvent strip which strips away the sidewall polymer residue124 and the photoresist mask 120, but leaves a polymer residue 126 asschematically illustrated in FIG. 4.

[0020] The wafer 30 is then mounted in the centrifuge carriage 28, asshown in FIG. 1. The centrifuge carriage 28 rotates the wafer 30 in thedirection indicated by arrow A. The first temperature control 15 heats asolvent in the first tank 14 to a temperature of between 50° C. and 100°C. In the preferred embodiment, the solvent is a N-methylpyrrolidine(NMP) based solvent heated to a temperature of between 65° C. and 85° C.The first valve 16 is opened and allows the NMP solvent from the firsttank to go to the spray nozzle 26, which sprays the NMP solvent into theprocessing chamber 12 and onto the rotating wafer 30. After a period oftime, the first valve 16 is closed, which discontinues the spraying ofthe NMP solvent from the first tank 14 into the processing chamber 12.

[0021] The second temperature control 19 maintains the solvent in thesecond tank 18 at a temperature of between 20° C. and 40° C. The solventin the second tank 18 is the same chemical as the solvent in the firsttank 14, which in the preferred embodiment the solvent is aN-methylpyrrolidine (NMP) based solvent, but is maintained at adifferent temperature, which in the preferred embodiment is between 25°C. and 30° C. The second valve 20 is opened and allows the NMP solventfrom the second tank 18 to go to the spray nozzle 26, which sprays theNMP solvent into the processing chamber 12 and onto the rotating wafer30. After a period of time, the second valve 20 is closed, whichdiscontinues the spraying of the NMP solvent from the second tank 18into the processing chamber 12. Since room temperature is within thetemperature range of the solvent in the second tank 18, the secondtemperature control 19 may not need to heat the solvent in the secondtank 18. Therefore, the invention may be practiced without the secondtemperature control 19. It is also possible that the second temperaturecontrol 19 may need to cool the solvent in the second tank 18 to keepthe solvent at room temperature.

[0022] The third temperature control 23 maintains water, which iscontained in the third tank 22, at a temperature of between 20° C. and40° C. The water is preferably kept at room temperature. The third valve24 is opened and allows the water from the third tank 22 to go to thespray nozzle 26, which sprays the water into the processing chamber 12and onto the rotating wafer 30. After a period of time, the third valve20 is closed, which discontinues the spraying of the water from thethird tank 22 into the processing chamber 12. Since the water ispreferably at room temperature, the third temperature control 23 may notneed to heat the water in the third tank 22. Therefore, the inventionmay be practiced without the third temperature control 23. It is alsopossible that the third temperature control 23 may need to cool thewater in the third tank 22 to keep the water at room temperature.

[0023] The centrifuge carriage 28 stops rotating the wafer 30. The wafer30 is removed from the centrifuge carriage 28. In the preferredembodiment, more than one wafer 30 is held in the centrifuge carriage 28at a time.

[0024]FIG. 5 is a cross sectional-view of the part of the unfinishedsemiconductor device 110 after it has been removed from the centrifugecarriage 28. The polymer residue 126 has been stripped from the stacks122. The inventive method is aggressive enough to provide a fastthroughput, but reduces solvent attack and corrosion of the firstrefractory metal layer 115, an aluminum alloy layer 116, and a secondrefractory metal layer 118.

[0025]FIG. 6 is a cross-sectional view of the part of the unfinishedsemiconductor device 110 after an intermetallic dielectric layer 130 hasbeen deposited over the stacks 122. Vias 132 have been etched in theintermetallic dielectric layer 130 to the stacks 122, using aphotoresist process. After the photoresist has been stripped, a polymerresidue 134 remains. The wafer 30 is placed into the centrifuge carriage28 as shown in FIG. 1, and the clean process described above isrepeated. Namely, the centrifuge carriage 28 rotates the wafer 30 in thedirection indicated by arrow A. The first temperature control 15 heats asolvent in the first tank 14 to a temperature of between 50° C. and 100°C. In the preferred embodiment the solvent is a N-methylpyrrolidine(NMP) based solvent heated to a temperature of between 65° C. and 85° C.The first valve 16 is opened and allows the NMP solvent from the firsttank to go to the spray nozzle 26, which sprays the NMP solvent into theprocessing chamber 12 and onto the rotating wafer 30. After a period oftime, the first valve 16 is closed, which discontinues the spraying ofthe NMP solvent from the first tank 14 into the processing chamber 12.

[0026] The second temperature control 19 maintains the solvent in thesecond tank 18 at a temperature of between 20° C. and 40° C. The solventin the second tank 18 is the same chemical as the solvent in the firsttank 14, which in the preferred embodiment the solvent is aN-methylpyrrolidine (NMP) based solvent, but is maintained at adifferent temperature, which in the preferred embodiment is between 25°C. and 30° C. The second valve 20 is opened and allows the NMP solventfrom the second tank 18 to go to the spray nozzle 26, which sprays theNMP solvent into the processing chamber 12 and onto the rotating wafer30. After a period of time, the second valve 20 is closed, whichdiscontinues the spraying of the NMP solvent from the second tank 18into the processing chamber 12. Since room temperature is within thetemperature range of the solvent in the second tank 18, the secondtemperature control 19 may not need to heat the solvent in the secondtank 18.

[0027] The third temperature control 23 maintains water which iscontained in the third tank 22 at a temperature of between 20° C. and40° C. The water is preferably kept at room temperature. The third valve24 is opened and allows the water from the third tank 22 to go to thespray nozzle 26, which sprays the water into the processing chamber 12and onto the rotating wafer 30. After a period of time, the third valve20 is closed, which discontinues the spraying of the water from thethird tank 22 into the processing chamber 12. Since the water ispreferably at room temperature, the third temperature control 23 may notneed to heat the water in the third tank 22.

[0028] The centrifuge carriage 28 stops rotating the wafer 30. The wafer30 is removed from the centrifuge carriage 28. In the preferredembodiment, more than one wafer 30 is held in the centrifuge carriage 28at a time.

[0029] The cleaning system 10 removes the polymer residue 134 from thevias 132. The inventive method is aggressive enough to provide a fastthroughput, but reduces solvent attack and corrosion of the secondrefractory metal layer 118, which is exposed to the solvent through thevias 132. Therefore the inventive polymer residue cleaning process maybe used to protect metal layers in both the production of stacks and inthe creation of vias.

[0030] The unfinished semiconductor device undergoes further processesknown in the prior art to complete the semiconductor device.

[0031] Information as herein shown and described in detail is fullycapable of attaining the above-described object of the invention, it isunderstood that it is the presently preferred embodiment of the presentinvention and is thus representative of the subject matter which isbroadly contemplated by the present invention, that the scope of thepresent invention fully encompasses other embodiments which may becomeobvious to those skilled in the art, and that the scope of the presentinvention is accordingly to be limited by nothing other than theappended claims, in which reference to an element in the singular is notintended to mean “one and only one” unless explicitly so stated, butrather “one or more”. All structural and functional equivalents to theelements of the above-described preferred embodiment that are known orlater come to be known to those of ordinary skill in the art areexpressly incorporated herein by reference and are intended to beencompassed by the present claims. Moreover, it is not necessary for adevice or method to address each and every problem sought to be solvedby the present invention, for it to be encompassed by the presentclaims. Furthermore, no element, component, or method step in thepresent disclosure is intended to be dedicated to the public regardlessof whether the element, component, or method step is explicitly recitedin the claims. No claim element herein is to be construed under theprovisions of 35 U.S.C. 112, sixth paragraph, unless the element isexpressly recited using the phrase “means for”.

We claim:
 1. A method of cleaning a semiconductor wafer, comprising thesteps of: placing the semiconductor wafer into a processing chamber;spraying a first solvent, maintained at a temperature between 50° C. and100° C., on to the semiconductor wafer; discontinuing the spraying ofthe first solvent on to the semiconductor wafer; spraying a secondsolvent, at a temperature between 20° C. and 40° C., on to thesemiconductor wafer; and discontinuing the spraying of the secondsolvent on to the semiconductor wafer.
 2. The method, as recited inclaim 1 , further comprising the step of: spraying water, at atemperature between 20° C. and 40° C., on to the semiconductor wafer,wherein the step of spraying water is after the discontinuing of thespraying of the second solvent on the semiconductor wafer.
 3. Themethod, as recited in claim 2 , wherein the first solvent and the secondsolvent are made of the same chemicals.
 4. The method, as recited inclaim 3 , further comprising the step of centrifuging the wafer duringthe steps of spraying the first solvent, spraying the second solvent,and spraying the water.
 5. The method, as recited in claim 4 , whereinin the step of spraying the first solvent, the first solvent is at atemperature between 65° C. and 85° C.
 6. The method, as recited in claim5 , wherein in the step of spraying the second solvent, the secondsolvent is at a temperature between 25° C. and 30° C.
 7. The method, asrecited in claim 6 , wherein the first solvent and the second solventare N-methylpyrrolidine.
 8. The method, as recited in claim 7 , furthercomprising the steps of: applying a layer on the semiconductor wafer,prior to placing the semiconductor wafer into the processing chamber;placing a resist mask on the layer, prior to placing the semiconductorwafer into the processing chamber; etching the layer, prior to placingthe semiconductor wafer into the processing chamber; and stripping theresist mask, prior to placing the semiconductor wafer into theprocessing chamber.
 9. The method, as recited in claim 8 , wherein partof the layer is metallic.
 10. The method, as recited in claim 8 ,further comprising the step of stripping a sidewall polymer residue,prior to placing the semiconductor wafer into the processing chamber.11. The method, as recited in claim 1 , wherein the first solvent andthe second solvent are made of the same chemicals.
 12. The method, asrecited in claim 11 , wherein in the step of spraying the first solvent,the first solvent is at a temperature between 65° C. and 85° C.
 13. Themethod, as recited in claim 12 , wherein in the step of spraying thesecond solvent, the second solvent is at a temperature between 25° C.and 30° C.
 14. The method, as recited in claim 13 , wherein the firstsolvent and the second solvent are N-methylpyrrolidine.
 15. An apparatusfor cleaning a semiconductor wafer, comprising: a processing chamber; awafer centrifuge mounted in the processing chamber, with a means forretaining a semiconductor wafer; a spray nozzle mounted within theprocessing chamber; means for providing a first solvent, at atemperature between 50° C. and 100° C., to the spray nozzle; means forproviding a second solvent, at a temperature between 20° C. and 40° C.,to the spray nozzle; and means for providing water, at a temperaturebetween 20° C. and 40° C., to the spray nozzle.